Specifically, the php_geoip.dll extension is not available in a pre-compiled form for Windoze PHP developers.

There are only two alternative solutions to self-compiling for Windoze (AFAIK):

1) Use the "Pure" PHP version of the GeoIP API from MaxMind available here (http://www.maxmind.com/download/geoip/api/php/). This solution is not really acceptable for production machines because of its slower speed. However, it does work for development.

2) Use the older version of this pre-compiled extension (http://www.gknw.de/php/ext_win32/php-5.2.1_geoip-w32.zip). It worked on my development system using Windoze XP sp2, Apache 2.2.3 and PHP 5.2.10. There are also older versions for PHP 5.1.2 and PHP 5.1.4 in the same directory.

This installs the library in /opt/local. Unfortunately the current version of the PECL extension doesn't know to look there, so you'll need to download and compile manually from http://pecl.php.net/package/geoip

If phpize complains that it cannot find files under /Applications/MAMP/bin/php5/include, make sure you have the development version of MAMP installed (link towards the bottom of the MAMP download page).

You're nearly there! The extension will have installed in /usr/lib/php. You need to copy it into your MAMP extension directory: